With technological development of light emitting devices (LEDs), cost reduction and energy saving are prevalent. In addition, more various devices utilizing light emitting devices (LEDs) are developed. Nowadays, although LEDs emitting visible light are actively utilized in application fields including lighting, ultraviolet (UV) light sources are widely used in scientific, agricultural, environmental and semiconductor industries and applications thereof will expand in the future.
A light emitting device (LED) is a device that converts electrical energy into light. In general, the LED includes one or more active layers including semiconductor materials interposed between a plurality of layers doped with opposite electrical properties. In general, holes and electrons are injected into the active layer when a bias is applied to two ends of the doped layers, the holes recombine with the electrons in the active layer, thus emitting light. The light is emitted from the entire surfaces of the active layer and the LED.